Inaccuracies in self-reports may lead to duplication of therapy, failure to appreciate non-compliance leading to exacerbation of chronic medical conditions, or inaccurate research conclusions. Our objective is to determine the accuracy of self-reported drug ingestion histories in patients presenting to an urban academic emergency department (ED). We conducted a prospective cohort study in ED patients presenting for pain or nausea. We obtained a structured drug ingestion history including all prescription drugs, over-the-counter medication (OTC) drugs, and illicit drugs for the 48 hours prior to ED presentation. We obtained urine comprehensive drug screens (CDS) and determined self-report/CDS concordance. Fifty-five patients were enrolled. Self-reported drug ingestion histories were poor in these patients; only 17 (30.9%) of histories were concordant with the CDS. For the individual drug classes, prescription drug-CDS was concordant in 32 (58.2%), OTC-CDS was concordant in 33 (60%), and illicit drug-CDS was concordant in 45 (81.8%) of subjects. No demographic factors predicted an accurate self-reported drug history. Sixteen patients had drugs detected by CDS that were unreported by history. Nine of these 16 included an unreported opioid. In conclusion, self-reported drug ingestion histories are often inaccurate and resources are needed to confirm compliance and ensure unreported drugs are not overlooked.